diff --git a/crates/dbx-core/src/models/connection.rs b/crates/dbx-core/src/models/connection.rs
index d726b7ab04..7535984142 100644
--- a/crates/dbx-core/src/models/connection.rs
+++ b/crates/dbx-core/src/models/connection.rs
@@ -121,7 +121,8 @@ impl ConnectionConfig {
                 if let Some(cs) = self.connection_string.as_deref().filter(|s| !s.is_empty()) {
                     return cs.to_string();
                 }
-                format!("mongodb://{host}:{port}{db_part}")
+                let suffix = if params.is_empty() { String::new() } else { format!("?{params}") };
+                format!("mongodb://{host}:{port}{db_part}{suffix}")
             }
             DatabaseType::Oracle => format!("oracle://{host}:{port}{db_part}"),
             DatabaseType::Elasticsearch => format!("http://{host}:{port}"),
@@ -172,10 +173,11 @@ impl ConnectionConfig {
                 if let Some(cs) = self.connection_string.as_deref().filter(|s| !s.is_empty()) {
                     return cs.to_string();
                 }
+                let suffix = if params.is_empty() { String::new() } else { format!("?{params}") };
                 if self.username.is_empty() {
-                    format!("mongodb://{host}:{port}{db_part}")
+                    format!("mongodb://{host}:{port}{db_part}{suffix}")
                 } else {
-                    format!("mongodb://{username}:{password}@{host}:{port}{db_part}")
+                    format!("mongodb://{username}:{password}@{host}:{port}{db_part}{suffix}")
                 }
             }
             DatabaseType::Oracle => {
@@ -233,9 +235,33 @@ impl ConnectionConfig {
                 }
             }
             DatabaseType::Postgres | DatabaseType::Redshift => value.trim_start_matches('?').to_string(),
+            DatabaseType::MongoDb => self.normalized_mongodb_url_params(value),
             _ => value.trim_start_matches('?').to_string(),
         }
     }
+
+    fn normalized_mongodb_url_params(&self, value: &str) -> String {
+        let mut params: Vec<String> = value
+            .trim_start_matches('?')
+            .split('&')
+            .filter(|param| !param.trim().is_empty())
+            .map(str::to_string)
+            .collect();
+
+        push_query_param_if_missing(&mut params, "directConnection", "directConnection=true".to_string());
+
+        if !self.username.is_empty() {
+            let auth_source = self.database.as_deref().filter(|db| !db.is_empty()).unwrap_or("admin");
+            push_query_param_if_missing(
+                &mut params,
+                "authSource",
+                format!("authSource={}", encode_url_part(auth_source)),
+            );
+            push_query_param_if_missing(&mut params, "authMechanism", "authMechanism=SCRAM-SHA-1".to_string());
+        }
+
+        params.join("&")
+    }
 }
 
 fn encode_url_part(value: &str) -> String {
@@ -250,6 +276,15 @@ fn bracket_ipv6(host: &str) -> String {
     }
 }
 
+fn push_query_param_if_missing(params: &mut Vec<String>, key: &str, value: String) {
+    if !params
+        .iter()
+        .any(|param| param.split_once('=').map(|(name, _)| name).unwrap_or(param.as_str()).eq_ignore_ascii_case(key))
+    {
+        params.push(value);
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::{ConnectionConfig, DatabaseType};
@@ -281,6 +316,13 @@ mod tests {
         }
     }
 
+    fn mongodb_config(username: &str, password: &str, database: Option<&str>) -> ConnectionConfig {
+        let mut config = mysql_config(username, password, database);
+        config.db_type = DatabaseType::MongoDb;
+        config.port = 17000;
+        config
+    }
+
     #[test]
     fn mysql_url_encodes_oceanbase_username() {
         let config = mysql_config("user@tenant#cluster", "secret", None);
@@ -321,6 +363,27 @@ mod tests {
         assert_eq!(config.connection_url(), "postgres://postgres:secret@10.1.2.3:2883/test?sslmode=disable");
     }
 
+    #[test]
+    fn mongodb_form_url_adds_legacy_direct_connection_params() {
+        let config = mongodb_config("root", "secret", Some("admin"));
+
+        assert_eq!(
+            config.connection_url(),
+            "mongodb://root:secret@10.1.2.3:17000/admin?directConnection=true&authSource=admin&authMechanism=SCRAM-SHA-1"
+        );
+    }
+
+    #[test]
+    fn mongodb_form_url_respects_custom_auth_params() {
+        let mut config = mongodb_config("root", "secret", Some("app"));
+        config.url_params = Some("authSource=admin&authMechanism=SCRAM-SHA-256&retryWrites=false".to_string());
+
+        assert_eq!(
+            config.connection_url(),
+            "mongodb://root:secret@10.1.2.3:17000/app?authSource=admin&authMechanism=SCRAM-SHA-256&retryWrites=false&directConnection=true"
+        );
+    }
+
     #[test]
     fn redacted_mysql_url_omits_credentials() {
         let config = mysql_config("user@tenant#cluster", "p@ss:word#1", Some("db/name"));
@@ -357,4 +420,18 @@ mod tests {
         assert!(!url.contains("default"));
         assert!(!url.contains("redis-secret"));
     }
+
+    #[test]
+    fn redacted_mongodb_url_keeps_compatibility_params_without_credentials() {
+        let config = mongodb_config("root", "secret", Some("admin"));
+
+        let url = config.redacted_connection_url();
+
+        assert_eq!(
+            url,
+            "mongodb://10.1.2.3:17000/admin?directConnection=true&authSource=admin&authMechanism=SCRAM-SHA-1"
+        );
+        assert!(!url.contains("root"));
+        assert!(!url.contains("secret"));
+    }
 }
diff --git a/src/components/connection/ConnectionDialog.vue b/src/components/connection/ConnectionDialog.vue
index e745668a6f..93e449e09e 100644
--- a/src/components/connection/ConnectionDialog.vue
+++ b/src/components/connection/ConnectionDialog.vue
@@ -401,7 +401,7 @@ async function testConnection() {
   isTesting.value = true;
   testResult.value = null;
   try {
-    const config: ConnectionConfig = { ...form.value, id: editingId.value || uuid() };
+    const config = connectionConfigForSubmit(editingId.value || uuid());
     const msg = await api.testConnection(config);
     if (runId !== testRunId) return;
     testResult.value = { ok: true, message: msg };
@@ -415,6 +415,14 @@ async function testConnection() {
   }
 }
 
+function connectionConfigForSubmit(id: string): ConnectionConfig {
+  const config: ConnectionConfig = { ...form.value, id };
+  if (config.db_type === "mongodb" && !mongoUseUrl.value) {
+    config.connection_string = undefined;
+  }
+  return config;
+}
+
 function resetTestState() {
   testRunId += 1;
   isTesting.value = false;
@@ -462,11 +470,11 @@ async function save() {
   resetTestState();
   try {
     if (editingId.value) {
-      const updated: ConnectionConfig = { ...form.value, id: editingId.value };
+      const updated = connectionConfigForSubmit(editingId.value);
       await store.updateConnection(updated);
       store.stopEditing();
     } else {
-      const config: ConnectionConfig = { ...form.value, id: uuid() };
+      const config = connectionConfigForSubmit(uuid());
       await store.addConnection(config);
       open.value = false;
       await nextTick();
@@ -757,6 +765,20 @@ async function browseSshKeyPath() {
                         :placeholder="t('connection.databasePlaceholder')"
                       />
                     </div>
+                    <div class="grid grid-cols-4 items-center gap-4">
+                      <Label class="text-right">{{ t("connection.urlParams") }}</Label>
+                      <Input
+                        v-model="form.url_params"
+                        class="col-span-3"
+                        placeholder="authSource=admin&authMechanism=SCRAM-SHA-1"
+                      />
+                    </div>
+                    <div class="grid grid-cols-4 items-start gap-4">
+                      <span />
+                      <p class="col-span-3 text-xs text-muted-foreground">
+                        {{ t("connection.mongoLegacyHint") }}
+                      </p>
+                    </div>
                   </template>
                 </template>
 
diff --git a/src/i18n/locales/en.ts b/src/i18n/locales/en.ts
index aae68e7528..1df26c9755 100644
--- a/src/i18n/locales/en.ts
+++ b/src/i18n/locales/en.ts
@@ -112,6 +112,8 @@ export default {
     sshKeyPathBrowse: "Browse",
     sshExposeLan: "Expose tunnel to LAN",
     dmCompatHint: "Requires DM PG compatibility mode (set COMPATIBLE_MODE=7 in dm.ini and restart)",
+    mongoLegacyHint:
+      "MongoDB form connections add directConnection automatically; authenticated connections default to the selected database as auth source (admin when blank) and SCRAM-SHA-1, which you can override here.",
     compatible: "Compatible",
     mainstream: "Popular",
     color: "Color",
diff --git a/src/i18n/locales/zh-CN.ts b/src/i18n/locales/zh-CN.ts
index a2885f03c8..65afdf5e2d 100644
--- a/src/i18n/locales/zh-CN.ts
+++ b/src/i18n/locales/zh-CN.ts
@@ -111,6 +111,8 @@ export default {
     sshKeyPathBrowse: "浏览",
     sshExposeLan: "允许局域网访问隧道",
     dmCompatHint: "需要开启达梦 PG 兼容模式（dm.ini 中设置 COMPATIBLE_MODE=7 并重启服务）",
+    mongoLegacyHint:
+      "MongoDB 表单连接会自动补充 directConnection；带用户名时默认使用当前数据库认证源（留空为 admin）和 SCRAM-SHA-1，可在此覆盖。",
     compatible: "兼容",
     mainstream: "主流",
     color: "颜色",